Mapping sea surface oil slicks using RADARSAT-2 quad-polarization SAR image

Polarimetric SAR decomposition parameters, average alpha angle ((alpha) over bar) and entropy (H) are estimated for oil-slick contaminated sea surfaces and slick-free conditions using a RADARSAT-2 quad-polarization SAR image. The values of H and (alpha) over bar within oil slick areas are significantly higher than those of the ambient sea surface, indicating the dominance of Bragg scattering for the slick-free ocean and non-Bragg scattering for the oil-slick area. In land classification, the conformity coefficient (mu) is often used to discriminate surface scattering with double-bounce or volume scattering. Based on this rationale, we also develop a method using mu as a logical scalar descriptor to map oil slicks under low-to-moderate wind conditions. The proposed method is assessed using a RADARSAT-2 quad-polarization SAR image of oil slicks in the Gulf of Mexico. Analysis shows that when mu is positive the sea surface is slick-free, whereas mu is negative for oil-slick areas. This method provides a simple and effective mapping technique for oil slick detection. Citation: Zhang, B., W. Perrie, X. Li, and W. G. Pichel (2011), Mapping sea surface oil slicks using RADARSAT-2 quad-polarization SAR image, Geophys. Res. Lett., 38, L10602, doi:10.1029/2011GL047013.